1. Field of the Invention
The present invention relates to cutting units of cutting devices, such as table cutting devices and portable cutting devices, and also relates to drive systems used for the cutting devices.
2. Description of the Related Art
In general, a table cutting device includes a table for accommodating a workpiece, and a cutting unit vertically movably supported on the table, so that the workpiece can be cut as the rotary cutting blade cuts into the workpiece by the downward movement of the cutting unit.
A portable cutting device includes a base for placing on a workpiece, and a cutting unit supported on an upper side of the base. The cutting unit has a rotary cutting blade having a lower portion protruding downward from the base, so that the rotary cutting blade can cut the workpiece as the base and the cutting unit move together along the upper surface of the workpiece.
According to both of the table cutting device and the portable cutting device, the cutting unit includes an electric motor serving as a drive source for driving the rotary cutting blade, and a reduction gear train for reducing the rotational speed of the electric motor. As a known art relating to a technique of driving the rotary cutting blade by the electric motor, U.S. Patent Publication No. 2002/0152867 teaches to increase a distance between a spindle having a circular cutting blade mounted thereon and a motor shaft of an electric motor by reducing the rotational speed of the electric motor in plural stages by a reduction gear train. This arrangement enables to increase a maximum cutting depth achieved by the cutting blade and to set a large inclination angle of a cutting unit during an inclined cutting operation with the cutting unit inclined laterally from a vertical position.
However, the technique of the above U.S. patent involves a problem that the gear chamber must have a large vertical length to cause insufficient lubrication of an upper region of a gear chamber accommodating the gear train, because lubrication oil sealingly contained within the gear chamber may flow downward within the gear chamber.
Therefore, there is a need in the art for a cutting unit capable of improving lubrication within the gear chamber.